Metallic substrates such as steel sheet which are produced in steel mills are treated shortly after manufacture to prevent rusting and corrosion of the sheet prior to being formed into the desired parts. Typically mill oils, such as FERROCITE 61 AUS available from Quaker Chemical Corp., DRAWCO FB 27 MC-1 available from Novamax Technologies, Inc., and MONTGOMERY DB 4265 available from Fuchs Lubricants Co. have been used for this purpose.
The mill oils are typically removed after the metallic substrates are formed into parts. Mill oils and film-forming materials, however, are often difficult to remove completely and can be incompatible with subsequently applied organic materials, for example, primer coatings, adhesives and sealants.
In place of mill oils, organic polymers have also been employed as passivating agents for steel sheet. These materials generally provide better corrosion resistance than do mill oils and are easier to remove. However, depending on the organic polymer used, small residual amounts can remain on the surface of the metallic substrate. Although compatible with most subsequently applied primer coatings, these organic polymer residues are often incompatible with subsequently applied adhesives and sealants which are used in the assembly of automobiles.
Temporary protective coating compositions are known in the art. U.S. Pat. No. 4,942,193 discloses a formable, weldable temporary protective coating for metallic substrates which comprises a neutralized acid or base-functional polymer prepared in the presence of a lubricating composition consisting essentially of a relatively high level of a wax. The coating is particularly useful to provide in-transit corrosion resistance.
U.S. Pat. No. 5,081,174 discloses a formable, weldable, removable coating for use on untreated metals comprised of a base-neutralized, acid fuctional copolymer, a wax lubricant and a removability enhancing material such as phosphoric acid present at additive levels to improve the removability of the coating from metallic substrates by aqueous alkaline cleaners. The coatings provide corrosion resistance, are formable and/or drawable, weldable by conventional means, and can be removed with alkaline cleaners.
U.S. Pat. No. 5,229,450 discloses formable, weldable temporary protective aqueous coating compositions useful in passivating untreated metallic substrates. The coatings are comprised of a neutralized acid or base-functional polymer and a lubricating composition in an amount sufficient to impart drawability and formability to the metallic substrates to which they are applied. The coatings provide corrosion resistance, are formable and/or drawable, and weldable by conventional means, and can be removed with alkaline cleaners.
Although the above-described temporary protective coatings provide excellent in-transit corrosion resistance, weldability and formability, the coatings are often incompatible with subsequently applied adhesives and sealants.
It has been found that by using a polymer having a relatively high level of acid functional monomer present, compatibility of the temporary protective coating with a wide variety of adhesives and sealants can be improved.